This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Background: While static and ventilated caging systems are both widely utilized in transgenic mouse production facilities, the effects of caging on mouse oocyte and progeny production have not been sufficiently analyzed. This study was designed to compare the oocyte yield of FVB and B6 mice on individual ventilated and static isolated cages. Methods: FVB and B6 mice were maintained in either static or ventilated cages. Females were subjected to superovulation by injections of FHS and hCG and placed with males. Ova were collected 44 hrs later. Results/Discussion: There appeared to be no differences in oocyte yield between FVB and B6 females or caging system. The average oocyte per female in the static vs. ventilated caging system was 18 vs. 21 in FVB and 31 vs. 31 in B6, respectively. We subsequently tested the females'oocyte yield when they were housed in different areas of the ventilated rack (VR). Animals in cages located at the bottom o the VR produced more oocytes than those animals placed at the middle or top of the rack. To further determine whether this location effect could influence the progeny yield, FVB and ICR dams - six groups per strain at two mice per cage, were paired with one male each. The breeder trios were housed at the middle or the bottom of VR, and their litters and litter size were tracked for one year. Dams housed at the bottom of the VR produced significantly more litters than those housed at the middle of the rack, which was mostly due to a longer life span. This information should prove useful for colony management for both transgenic mouse production and general breeder colony maintenance.